The present invention relates generally to lubricants. In particular the present invention relates to a solid lubricant which comprises a copper-nickel-tin alloy ultra fine particles.
It is well-known that adding a solid lubricant such as powdery graphite or P.T.F.E. (Polytetrafluoroethylene), tungsten disulfide, molybdenum disulfide, etc. to a working surface leads to enhancing the lubricating properties of the surface; such as preventing of scoring of the contacting surface due to frictional heat and improvement of wear resistance at high temperatures and under high pressures.
Coupled with a wide diversity in the compositions themselves, various different techniques have been invoked in distributing and applying the lubricant to the areas to be treated. Such techniques have conventionally included incorporation of the lubricating material in various physical forms including oils and greases, as well as oil and grease compositions in which solids such as graphite, molybdenum disulfide, P.T.F.E., etc. have been dispersed or suspended. The benefits of solid particle lubricant additives are based on the so called cushioning effect i.e., the solid particles act as a cushion between sliding metal surfaces.
However, there are several problems associated with the use of the above mentioned solid lubricants. For instance when a sulphur compound is added, the additive and the contacting surface chemically react to the frictional heat and induce oxidation and corrosion of the contacting surface. This results in an increase in wear of the contacting surface. When an organic high molecular weight material such as P.T.F.E. is used, the product has inferior heat conductivity and heat stability.
Furthermore, when a powdery graphite is used, it is known that the lubricating properties deteriorate unless a water absorbing layer is contained in the thin molecular surface. On the other-hand, corrosion of the metal surface is induced in the presence of water.
Also, the preparation of stable dispersions of the solid lubricants mentioned above through chemical stabilization is a very complex problem. Moreover, the dispersions achieved by the chemical stabilization methods are short-lived. Upon standing for a short period of time, the particles settle due to gravitation and may even develop what is called a "hard settle", i.e., the particles cannot be redispersed.
A method of applying a high lubricity film as a friction-reducing surface coating formed by means of disintegrating of a pellet consisting of an intimate mixture of a finally divided powdery tin-lead type alloy and a molybdenum disulfide is described in U.S. Pat. No. 3,994,697 to Burke. However this solid lubricant is distributed by fuel of an internal combustion engine and can be delivered only to the fuel contacting parts of the engine. Furthermore the requirement for the pellet to be susceptible to abrasion within the fuel tank makes the disintegration process irregular and dependent upon many uncontrolled parameters.
A fine powder alloy used for an oil-impregnated bearing which contains a solid lubricant and phosphorus having a high reactivity with said solid lubricant and high oil content is disclosed in U.S. Pat. No. 4,274,874 to, Obara et al. This patent teaches sintering of a copper tin type powder alloy with 20 to 80 .mu.m molybdenum or tungsten disulfide particles acting as a solid lubricant. However, this patent is for production of a bearing material impregnant with lubricant oil that reduces the friction at the metal-to metal contact portion between a rotating shaft and the bearing rather than for a formation of a solid lubricant coating film for surface boundary lubrication.
Therefore it is a goal in the art to provide a more stable dispersion of particle type lubricants which do not suffer from the limitations noted above.
It is also goal in the present invention to provide an effective solid lubricant which acts as a solid lubricant and as a surface bonding plating.
It is also a goal in the present invention to provide a lubricant which is not appreciably affected by high temperatures or high pressures and is more advanced than conventional solid and liquid lubricants.